APC-M2 pAb recognizes endogenous APC protein in normal mouse intestinal tissue. Confocal immunofluorescence microscopy of cryosections from wild-type mouse ileum triple-labeled with APC-M2 pAb (green), β-catenin mAb (red) and DNA dye topro-3 (blue). Tissues are oriented so that luminal surfaces are at the top of the images. (A) An increasing gradient of APC staining from crypts to villus tips is apparent at this magnification. (B) Enlarged image of a region at the villus tip shown in (A). APC staining is concentrated in basolateral regions of villus epithelial cells. Scale bars, 20 μm.